<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>下拉菜单</title>
<link rel="stylesheet" href="css/bootstrap.min.css">
<link rel="stylesheet" href="style.css">
<style>
  .red{
    border: 1px solid red;
  }
  #tip{
    width:200px;
    height: 200px;
    position: absolute;
    top:100px;
    left: 100px;
  }
  .menu{
    border: 1px solid blue;
  }
  .menu li{
    cursor:pointer
  }
</style>
</head>
<body>

<button id="btn">dianji</button>


  <script src="js/jquery.min.js"></script>
  <script src="js.js"></script>
</body>
</html>